assume cs:code


code segment

    mov bx, 0
    mov cx, 12
    mov dx, 0

    mov ax, 0ffffH
    mov ds, ax

s:
    mov dl, ds:[bx]
    push ds
    mov ax, 0020H
    mov ds, ax
    mov ds:[bx], dl
    pop ds
    inc bx
    loop s


    mov ax, 4c00H
    int 21H

code ends

end